1. Field of the Invention
The present invention relates to a process and an apparatus for measuring sizes of steel sections such as H-sections, I-sections and the like, and more particularly to a process and an apparatus for size measurement capable of continuously and accurately measuring sizes of the steel section not only at a static state but also at a running state (hot rolling, cold rolling and the like). Further, the invention relates to a process and an apparatus for calibrating a laser range finder used for the size measurement of the steel section.
2. Description of Related Art
Heretofore, the measurement of sizes such as flange width, flange thickness, web thickness, deviation at center and the like in steel sections such as H-section, I-section and so on has mainly been carried out by manual measurement using vernier calipers, dial gauge or the like because of various shapes of the steel sections. However, such a manual measurement has drawbacks that the reproducibility is poor due to the difference among individuals, and the measurement takes a long time and the like. Therefore, it is strongly demanded to develop automatic measurement for the size of the steel section.
For this purpose, there have been disclosed the measurement of deviation at center in Japanese patent laid open No. 57-110901, measurement of sizes in H-sections such as deviation at center (web deviation) and the like in Japanese Patent laid open No. 57-144404, measurement of deviation at center and flange width in Japanese Patent laid open No. 58-179515, respectively, as a process for continuously measuring sizes of H-sections during the running at the hot rolling step.
In Japanese Patent laid open No. 57-110910, however, an ultrasonic rangefinder of water column system is used, so that in order to measure a maximum value of flange width in the steel section to be measured, it is required to considerably increase a guiding accuracy for the prevention of rolling of the section. Since the diameter of the water column is practically about 20 mm, if the rolling of the section to be measured is caused, the position to be measured is shifted and the measurement becomes impossible. Further, water used for the measurement gets on the surface of the web portion during the measurement to promote the cooling of the web and hence the temperature difference between the web portion and the flange portion becomes large. As a result, there are caused problems that the waving of the web portion is caused in the H-sections having thin web thickness and rust occurs in the web portion due to the above water leakage.
In Japanese Patent laid open No. 57-144404, a method of cutting lights from up and down directions and right and left directions is used as a measuring system, so that the measuring accuracy is bad and also the calculation accuracy on deviation at center and the like naturally becomes poor. Further, it is difficult to conduct the measurement under an atmosphere containing water droplets, steam or the like, so that there is caused a problem in the measurement at a position close to a rolling mill (for hot rolling).
In Japanese Patent laid open No. 58-179515, the flange width is detected by means of an image sensor such as CCD (charge coupled device) or the like attached to a box type bridge guide and also the deviation at center and web thickness are calculated from values measured by a water stream ultrasonic range finder attached to the same bridge guide. In this case, it is required to guide the steel section to be measured into the inside of the bridge guide, but there is no room against the rolling of the section during the passing through the bridge guide. For this end, the bridge guide itself is made rigid and the guiding at entrance and delivery sides is ensured to prevent the rolling of the section, otherwise there is caused a fear of damaging the equipment. Moreover, even if the equipment is strengthened, the measuring accuracy may lower due to vibrations of the bridge guide and sensors attached thereto.
In the aforementioned references, the maximum value of flange width is not measured while exactly taking an edge shape of the flange portion, so that the measuring accuracy is fundamentally poor.
In Japanese Patent laid open No. 2-254304 is proposed an apparatus for the shape measurement of steel sections comprising a pair of stage mechanisms arranged so as to sandwich the steel section from up and down directions and moving toward horizontal and vertical directions, laser displacement meters attached to the stage mechanisms and detecting vertical and horizontal positions of the steel section, and a data processing device calculating the shape of the steel section from values detected by the laser displacement meters.
In the above apparatus, however, the flange widths, flange thicknesses, web thicknesses and the like at right and left sides of the steel section are measured while moving three pairs of up and down laser displacement meters inside a frame, so that the time is considerably taken for continuously measuring the steel section at an on-line state and hence the measurement becomes inefficient.
In the size measurement of the steel section, it is required to measure the maximum value of flange width and deviation at center with a high accuracy by exactly taking the edge shape of the flange portion even if the steel section to be measured causes the rolling phenomenon during the running at the hot rolling line.
In this connection, the flange portion of H-sections takes various edge shapes as shown in FIGS. 1a to 1d. On the other hand, if the rolling is caused in the running steel section during the measurement, it can not completely be controlled. Therefore, even if the rolling is caused, it is important to exactly take the edge shape of the flange portion in the steel section in order to accurately measure the maximum value of the flange width.
Here, the deviation at center S of the H-section is a value calculated from foot lengths b.sub.1, b.sub.2 in FIG. 2 according to the following equation: EQU S=(b.sub.1 -b.sub.2)/2
Therefore, in order to obtain the value of the deviation at center S with a high accuracy, it is important to accurately measure the foot lengths b.sub.1, b.sub.2 by exactly taking the edge shape of the flange portion.
As to thick or thin sheets, it is possible to measure only the thickness of the sheet at an on-line state for hot rolling as described, for example, in Japanese Patent laid open No. 59-183315 and No. 61-17008. However, such a measurement of the sheet thickness is naturally unsuitable for measuring the size of the steel sections because these sections have many sizes to be measured such as web height, flange width, deviation at center and the like and also because the measuring positions change for each series of rolling line.
In this connection, if many sensors are used, the measurement is possible, but there are many difficulties in view of the setting space for the sensors and the processing of signals therefrom and the cost becomes increased. Therefore, apparatuses for measuring multi-dimensional sizes at hot state do not yet come into practical use.
In order to measure the sizes of hot rolled steel sheets such as steel sections at hot state in the hot rolling line, it is first required that the measurement on many sizes of the steel section such as flange height, flange width, deviation at center and the like is adapted to fluctuations of rolling size and rolling series. In addition, it is required that the measurement apparatus has a room for accepting the warp or bending of the section (about 20 mm in each of up and down and right and left directions) and further the apparatus is escaped toward an off-line position in case of conducting no measurement to prevent the occurrence of troubles such as kicking and the like.
Recently, a laser rangefinder is frequently used when the sizes of the steel section such as H-sections, I-sections and the like are measured even in the conventional techniques as mentioned above. In this case, it is required to rapidly calibrate the laser rangefinder for adequately measuring the sizes of the steel section irrespectively of static state or on-line state for hot rolling or cold rolling. The term "calibration" used herein is a general meaning for determining a relation between a value indicated by the measuring device and a true value using a standard device and standard specimen. Moreover, a disc-shaped calibrating member is used as the above standard device and specimen.
For example, a method of calibrating the laser rangefinder is disclosed in Japanese Patent laid open No. 2-115711. This is a system that the calibration of the laser rangefinder is carried out by irradiating a laser beam to the surface of the calibrating member, and a distance ranging from the calibrating member to the laser rangefinder is carried out by determining a moving distance along a linear guide through a high accuracy distance detecting device such as a magnetic scale or the like. However, this system can not be adopted for a case that the measurement is carried out by properly changing the distance toward the steel section to be measured under such a circumstance that the magnetic scale is arranged close to the rolling mill (particularly influence of vibrations) from a view point of the calibrating time and calibrating accuracy, so that it is only used as a calibration method at an off-line state before the incorporation into an existing machine.
Furthermore, the calibration of a thickness indicator is disclosed in Japanese Patent laid open No. 59-54913. This calibration is applied to thickness indicators using a radiation source such as .gamma.-ray or the like. In this case, however, a procedure for intermittently rotating the calibrating member having a stepwise thickness for each given angle becomes troublesome. Moreover, when using the laser rangefinder (which has a small beam spot size and is dependent upon the measuring cycle speed), the measurement is largely influenced by the roughness of machined surface in the calibrating member (surface roughness) and the rotating speed of the calibrating member (speed passing on flat portion), so that there are many problems from a viewpoint of the accuracy, which is not disclosed in this reference.
If it is intended to measure various sizes of the steel section at once by using the laser rangefinder, the acceptable time for the calibration of the laser rangefinder at on-line state is restricted by rolling pitch and the like, and also it is required to make the calibrating time per one sensor minimum.
Various sizes of the steel section to be measured are shown in FIG. 2. In general, the flange width B is 150-520 mm, and the web height H is 300-940 mm. In the apparatus for the size measurement of steel sections arranged close to the rolling mill, therefore, it is important how to calibrate the linearity of such a size range with a high accuracy for a short time. In any case, the calibration of the laser rangefinder arranged close to the mill is dependent upon how to accurately measure the distance up to the surface of the section to be measured. However, in the aforementioned calibration, the high accuracy linear scale (e.g. magnetic scale or the like) moves under environment, particularly vibration during the measurement to lower the accuracy.